Underground mines have proven to be resistant to wireless communication due to environmental conditions that limit the transmission of radio waves. Typical radio waves used in wireless communications can only propagate a few feet before they are absorbed, diffracted, or reflected from rocks, walls, and other objects in the mine. Thus, most mines have hardwired communication systems, referred to as leaky coax cable systems.
However, hardwired communication systems are vulnerable to explosions, fire or cave-ins—all of which will tend to cut off communications with both the rest of the mine, as well as with aboveground parties. In addition, such hardwired systems are particularly susceptible to being run over by the heavy equipment moving in and out of the mine. Underground communications also tend to require the frequent relocation of communication access points. That, coupled with the already harsh conditions, leads to high system maintenance costs as well as unacceptable risks associated with loss of communications.
As such, there has been an increased interest in providing wireless communication solutions for underground communication applications, as well as other applications in which hardwired systems are susceptible. However, providing a mobile wireless solution capable of delivering continuous communication to such an environment has proved elusive.